Eid JE, Sollner-Webb B. ST-2, a telomere and subtelomere duplex and G-strand binding protein activity in Trypanosoma brucei.
J Biol Chem 1997;
272:14927-36. [PMID:
9169464 DOI:
10.1074/jbc.272.23.14927]
[Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
From Trypanosoma brucei, we identified ST-2, a protein complex that interacts with telomeric DNA and exhibits novel features. It binds specifically to the double-stranded telomere repeats (TTAGGG) and more tightly to the subtelomere 29-base pair elements that separate the telomere repeats from their proximal telomere-associated sequences. Interestingly, ST-2 showed still greater affinity for the G-rich strand of the telomere present either as an overhang or in a single-stranded form, but it exhibited the highest affinity for the G-rich strand of the subtelomere repeats. The binding characteristics of ST-2 are complementary to those of ST-1, a 39-kDa polypeptide we previously identified in T. brucei (Eid, J., and Sollner-Webb, B. (1995) Mol. Cell. Biol. 15, 389-397) that binds preferentially to the C-rich strands of the subtelomere and telomere repeats. UV cross-linking revealed five polypeptides of ST-2 that bind directly to the G-rich strand of the DNA, one of which is phosphorylated. Furthermore, the presence of ST-1 is critical for ST-2 complex binding both to the G-rich strand and to the duplex DNA, evidently as part of the ST-2 complex. This indicates that when binding to the duplex subtelomere and telomere repeats, ST-2 may act as a protein bridge with its ST-1 subunit binding to the C-rich strand and its five other cross-linkable polypeptides binding to the G-rich strand. Such an association could serve to hold the genomic subtelomeric and telomeric sequences in a partially single-stranded configuration to facilitate the recombinational events in this region that are crucial to the parasite.
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